In multi-cylinder engines, it is sometimes difficult to determine which cylinder is not performing optimally. Advances in electronic fuel injection controls and electronic controls in diesel engines have made it easier to control the fuel injection and compression in each cylinder to help in determining of which cylinder is not working. There are two common reasons for a cylinder not providing any power in a diesel engine. Either the fuel system is not providing fuel needed for proper combustion, or the compression is inadequate to initiate combustion of the fuel and air mixture.
However, it is difficult to determine sub par performance of a weak cylinder. Diagnostics have been developed to determine which cylinder in diesel engines are underperforming. The diagnostics are made by shutting off fuel to various combinations of cylinders and comparing the various readings of power output due to different cylinders. However, while these diagnostics determine which cylinder is underperforming, they do not determine the cause for the sub-par performance until after partial disassembly. It is thus often impossible to determine the nature and extent of the repair to the diesel engine and to render an estimate as to time needed for the repair and the expense involved. For example, the repair to the fuel system is quite different than the repair for faulty compression. The repair to a fuel system such as replacing a fuel injector may take a one or two hours. On the other hand, repairing the rings in a cylinder to fix it compression ratio may take over twenty hours of time. Up till now, there has been no diagnostic to determine if the cylinder needs repair to the fuel system or repair to its rings to fix its compression.
Engine brakes have long been used on diesel engines. One engine brake often referred to as a “Jake” brake is based on the fact that it takes energy to compress the air in the cylinder during the compression stroke. Most of this energy is recaptured during the power stroke as the compressed air functions as a spring to help the piston move in its power down stroke. When a jake brake is in effect, the fuel is shut off to the cylinder. To increase the brake effect, the spring rebound effect on the piston, the compressed air is allowed to escape through the exhaust manifold by opening of the exhaust valve near the end of the compression stroke. Thus any stored energy is thus lost and the braking effect on the engine is increased. However, engine brakes have not been used for diagnosing engine performance.
What is needed is a diagnostic method to determine if failure and poor performance of a cylinder in a diesel engine is fuel related or compression related. What is also needed is a diagnostic system that incorporates the engine brake.